This application claims the benefit of a Japanese Patent Application No. 11-250040 filed Sep. 3, 1999, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to redundant monitoring control systems, monitoring control apparatuses therefor and monitored control apparatuses, and more particularly to a redundant monitoring control system which carries out remote monitoring and control of monitored control apparatuses such as communication apparatuses which form a communication network, by switching a working one of monitoring control apparatuses which form a redundant structure. The present invention also relates to a monitoring control apparatus which includes a means of switching the monitoring control to another monitoring control apparatus, and to a monitored control apparatus which is monitored controlled by such a monitoring control apparatus.
Communication systems form a basis of society, and if a failure is generated in a communication network to interrupt a communication service, damages caused thereby spread over a wide range. For this reason, there are demands to minimize the failure in the communication systems.
In order to cope with such demands, a monitoring control apparatus is provided to constantly monitor the state of the communication network. The monitoring control apparatus detects the generation of the failure in the communication network at an early stage, and takes appropriate measures against the detected failure, so as to prevent a situation where a serious failure such as the interruption of the communication service is generated.
However, if the monitoring control apparatus itself fails, it becomes impossible to monitor the state of the communication network. Hence, in order to enable constant monitoring and control of the communication even when the monitoring control apparatus itself fails, a plurality of monitoring control apparatuses are provided to carry out the monitoring and control of the communication network by use of a redundant structure.
According to the redundant structure which uses the plurality of monitoring control apparatuses, the working monitoring control apparatus which actually monitors and controls the communication network is switched to another backup monitoring apparatus which operates normally if the working monitoring control apparatus fails, so that after the switching, the communication network is similarly monitored and controlled by the backup monitoring control apparatus.
2. Description of the Related Art
According to the conventional monitoring and control system employing the redundant structure, an operator of the monitoring control apparatus manually switches from the working monitoring control apparatus to the backup monitoring control apparatus when a failure is generated in the working monitoring control apparatus. That is, the operator manually switches the connection from the working monitoring control apparatus to the backup monitoring control apparatus, resumes the monitoring and control of the communication network by the backup monitoring control apparatus, and continues the monitoring and control operation.
On the other hand, instead of employing the redundant structure which uses the plurality of monitoring and control apparatuses, it is possible to construct the monitoring control apparatus by a high-reliability computer which can internally realize a redundant function. But in this case, it is necessary to use an expensive and special computer, which makes the hardware of the monitoring control apparatus itself expensive. As a result, the cost of the communication system as a whole which uses such an expensive monitoring control apparatus inevitably becomes high.
Because the conventional monitoring and control system which has the redundant structure by use of the plurality of monitoring control apparatuses requires the operator to manually switch from the working monitoring control apparatus to the backup monitoring control apparatus when the working monitoring control apparatus fails, it takes a relatively long time for the operator to recognize the failure of the working monitoring control apparatus, switch the connection to the backup monitoring control apparatus, resume the monitoring and control by the backup monitoring control apparatus, and continue the monitoring and control operation. Consequently, a state in which the communication network is not monitored continues for the relatively long time, thereby causing a delay in detecting a failure which is generated in the communication network during this time, and a long interruption of the control which is necessary with respect to the communication network. Therefore, the interruption and the like of the communication service is generated, and there is a problem in that the communication service deteriorates.
Particularly, it takes a long time to carry out a control operation such as downloading from the monitoring control apparatus data which are necessary to normally operate the monitored control apparatus such as a communication apparatus which forms the communication network. For this reason, such a control operation is often reserved to be carried out at a time during the night when the operator is not present. But when the monitoring control apparatus fails during such a control operation carried out at night, the operator must manually switch the working monitoring control apparatus to the backup monitoring control apparatus the next morning. Consequently, the failure of the working monitoring control apparatus cannot be corrected quickly, and there is a problem in that it is difficult to provide a stable communication service particularly during busy hours.
Accordingly, it is a general object of the present invention to provide a novel and useful redundant monitoring control system, monitoring control apparatus therefor and monitored control apparatus, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a redundant monitoring control system, monitoring control apparatus therefor and monitored control apparatus, which can automatically switch from a working monitoring control apparatus to a backup monitoring control apparatus when a failure is generated in the working monitoring control apparatus and continue the monitoring and control operation, without the need for an operator to manually carry out such operations.
Still another object of the present invention is to provide a redundant monitoring control system comprising at least one monitored control apparatus forming a communication network, a plurality of monitoring control apparatuses monitoring and controlling the monitored control apparatus, means, provided in the monitored control apparatus, for switching a monitoring and control of the monitored control apparatus by a monitoring control apparatus of a working system to a monitoring control apparatus of a backup system in response to a disconnection from the monitoring control apparatus of the working system which is detected when the monitoring control apparatus of the working system fails, and means, provided in the monitoring control apparatus of the backup system, for recognizing a control operation carried out by the monitoring control apparatus of the working system until the switching, and carrying out a remainder of the recognized control operation with respect to the monitored control apparatus. According to the redundant monitoring control system of the present invention, the control information is transferred to one of the monitoring control apparatuses which form a redundant structure, in response to the generation of the failure in the monitoring control apparatus of the working system. In addition, the monitoring and control of the monitored control apparatus is taken over by the monitoring control apparatus of the backup system. As a result, it is possible to continue the monitoring and control of the monitored control apparatus even when the monitoring control apparatus of the working system fails, without requiring a manual operation of the maintenance operator.
The redundant monitoring control system may further comprise means, provided in the monitored control apparatus, for establishing a connection to the monitoring control apparatus of the backup system when the disconnection to the monitoring control apparatus of the working system is detected, and means, provided in the monitored control apparatus, for notifying the control operation carried out by the monitoring control apparatus of the working system until the failure to the monitoring control apparatus of the backup system.
The redundant monitoring control system may further comprise means, provided in the monitoring control apparatus of the backup system, for establishing a connection to the monitoring control apparatus of the working system and successively acquiring monitored information and control information related to the monitored control apparatus from the monitoring control apparatus of the working system, and means, provided in the monitoring control apparatus of the backup system, for monitoring a state of the monitoring control apparatus of the working system, and when a failure of the monitoring control apparatus of the working system is detected, establishing a connection with respect to the monitored control apparatus and taking over the control operation carried out by the monitoring control apparatus of the working system until the failure.
In the redundant monitoring control system, the plurality of monitoring control apparatuses which are provided with respect to each monitored control apparatus may be grouped to distribute load of processing with respect to each monitored control apparatus.
A further object of the present invention is to provide a monitored control apparatus which establishes a connection to a monitoring control apparatus of a working system and is monitored and controlled by the monitoring control apparatus of the working system, comprising means for establishing a connection to a monitoring control apparatus of a backup system when a disconnection of the connection to the monitoring control apparatus of the working system is detected, and means for notifying to the monitoring control apparatus of the backup system a control operation carried out by the monitoring control apparatus of the working system until the disconnection, so that monitoring and control of the monitored control apparatus are taken over by the monitoring control apparatus of the backup system after the disconnection.
Another object of the present invention is to provide a monitoring control apparatus for monitoring and controlling a monitored control apparatus via a connection which is established between the monitoring control apparatus and the monitored control apparatus, comprising means for receiving control information which is related to control carried out by an other monitoring control apparatus and is notified from the monitored control apparatus, and means for taking over the control carried out by the other monitoring control apparatus based on the control information.
Still another object of the present invention is to provide a monitoring control apparatus for monitoring and controlling a monitored control apparatus via a connection which is established between the monitoring control apparatus and the monitored control apparatus, comprising means for successively notifying monitored information and control information related to the monitored control apparatus to an other monitoring control apparatus of a backup system when the monitoring control apparatus operates as a working system, and means for taking over a control operation carried out by an other monitoring control apparatus of a working system with respect to the monitored control apparatus based on control information notified from the other monitoring control apparatus of the working system when the monitoring control apparatus operates as a backup system and a disconnection of the monitoring control apparatus from the other monitoring control apparatus of the working system is detected.
The monitoring control apparatus may be grouped with a plurality of monitoring control apparatuses which are provided with respect to the monitored control apparatus so as to distribute load of processing with respect to the monitored control apparatus.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.